1. Field of the Invention
Exemplary embodiments of the present invention relate to a display substrate and a method of manufacturing the display substrate. More particularly, exemplary embodiments of the present invention relate to a display substrate including a thin-film transistor and a method of manufacturing the display substrate.
2. Discussion of the Background
Generally, a thin-film transistor (TFT) includes an active pattern forming a channel between a source electrode and a drain electrode. The active pattern may include amorphous silicon (a-Si), polysilicon (p-Si), oxide semiconductor, etc. An amorphous silicon layer may be easily formed on a large-sized substrate. However, an electron mobility of the amorphous silicon layer is about 0.5 cm2/Vs so that a driving characteristic of the TFT is not very good. A poly-silicon layer has an electron mobility, which is tens to hundreds of cm2/Vs greater than the amorphous silicon layer. However, it is difficult to uniformly form the poly-silicon layer on a large-sized substrate, and manufacturing costs for forming the poly-silicon layer are high. The oxide semiconductor has an electron mobility of tens to hundreds of cm2/Vs and is easily formed on large-sized substrates. In addition, the oxide semiconductor is formed at a low temperature. Thus, the oxide semiconductor has received attention as a semiconductor to replace the amorphous silicon layer or the poly-silicon layer.
Meanwhile, a plurality of patterns of a display substrate are formed using a photolithography process. When the number of masks used for the photolithography process is decreased, the purchase cost of the masks may be decreased. In addition, at least one of an exposure process, a developing process, an etching process and/or a strip process may be omitted to decrease the manufacturing cost and to improve the productivity.
However, when an oxide semiconductor TFT has a structure substantially the same as that of a conventional TFT structure including the a-Si or the p-Si of a bottom gate, the oxide semiconductor layer may be damaged in forming the oxide semiconductor TFT. For example, when the oxide semiconductor layer, and the source and drain electrodes are formed is using a single mask, the oxide semiconductor layer is easily damaged in forming the source and drain electrodes.
In order to solve the above-mentioned problem, a structure including an etch-stopper protecting the oxide semiconductor layer is applied to the oxide semiconductor TFT. However, an additional mask for forming the etch-stopper is needed in forming the oxide semiconductor TFT. Thus, decreasing the number of masks used for forming the oxide semiconductor TFT is limited. In addition, when the oxide semiconductor layer, and the source and drain electrodes are formed using a single mask, forming the source and the drain electrodes is more complicated to prevent damage to the oxide semiconductor layer.